This invention relates to a planar contact grid array connector having a metal substrate selectively coated with a ceramic, in combination with ceramic thick film and/or multi-layer thin film circuitry and contacts which may be affixed to or incorporated in mating connector halves.
Planar contact grid array connectors of the type described feature the following characteristics: increased power handling capability; improved means for effecting gas-tight contact between mating connector halves; a more rugged, more reliable, lighter and smaller connector than has heretofore been known; coaxial connection features; and integral means for electromagnetic interference (EMI) filtering, impedance control and signal/power conditioning.
Connectors of various types are used to interconnect electrical and electronic devices, assemblies, units, etc. These connectors are available in various geometric configurations, i.e. cylindrical, rectangular, etc., and incorporate various means for electrically connecting and disconnecting circuit paths. Some connector types incorporate integral means for EMI filtering and signal/power conditioning.
The prior art connectors suffer certain disadvantages such as: limited life in terms of connect and disconnect (mate and unmate) cycles; deformation of mating parts; contamination of conducting surfaces; foreign material occluded in connector cavities; large insertion and extraction forces, often beyond manual capabilities; large spacing between adjacent connection points; and the requirement for special repair and inspection tools.
Electromechanical devices, such as relays, have long used contacts which may be electroplated on and/or mechanically affixed to compliant meeting parts, often referred to as contact leads. These contact arrangements generally provide good and long term reliability in terms of gas-tight connections.
Electroplated spherical "gold bumps" have long been applied in grid type patterns to the surfaces of various substrates, i.e. printed circuit boards, ceramic integrated circuit chip carriers, etc. Such arrangements are frequently used for permanently connecting electrical and electronic components via lead wires or beams to circuit paths on or in the substrates.
Compression type interconnect systems or planar contact grid array connectors employ the aforenoted types of contacts and electroplated spherical gold bumps. One such interconnect system is that developed and marketed by the Connecting Devices Division of the Hughes Aircraft Company under the trade designation GOLD DOT. The GOLD DOT connector and a connector marketed by TRW Company, Inc. under the trade designation BUTTON BOARD differ substantially from arrangements employed for other connectors intended for repetitive insertions (matings) and extractions (unmatings).
The compression connector arrangements described above and, in particular, the GOLD DOT arrangement is based on clamping a spherical noble metal contact, which may be an electrically deposited gold bump, on the surface of one mating part against a corresponding noble metal or metal plated pad on the mating component. These dots and pads are precisely arranged in grid type, mirror image patterns on their respective mating components. In use, a minimum of four ounces of clamping force is required for a gas-tight contact or seal. Therefore, a reasonably sized connector with 400 contacts requires a total of 1600 ounces or 100 pounds of force. Small variations in contact surface height must be accommodated and the total force must be borne uniformly by each contact pair. In the instant case, each of the 400 contacts must experience a minimum of 4 ounces of force to assure a gas-tight connection. This requires that one of the mating connector halves be sufficiently rigid to resist deformation induced by the forces concentrated on contact surfaces. The other connector half must have sufficient compliance so that the individual forces are concentrated on the contact surfaces, rather than between said surfaces. Also, this compliance must accommodate small variations in the height of contact surfaces to avoid non-uniform distribution of forces among individual contacts.
In the case of the Hughes GOLD DOT connectors, the mating parts that support the bumps or dots are made of materials usually used for flexible printed circuits. External connection points and conducting paths to the dots are also provided on this flexible substrate material. The corresponding mating part with the pads or bumps may be made of flexible printed circuit board material, rigid or semi-rigid printed circuit board material, or ceramic substrate material. Also, the corresponding part contains the conducting paths between the pad and external connection points.
Unlike most other interconnect systems, the Hughes GOLD DOT or other compression contact connectors do not require large forces during connector engagement and disengagement because the contacts do not "wipe" each other. That is to say, there is no mechanical interference involved. To make reliable, low resistance connections, i.e. gas-tight connections, the two halves of the connector are precisely aligned and a large compression force is applied with a clamping type mechanism. Like several low signal or instrumentation type electric relay contacts, the resulting pressure at each of the dot/pad connection points is usually large enough to break any contaminating film or oxide on either or both surfaces and is sufficient to assure low electrical resistance paths.
Although the Hughes GOLD DOT interconnect arrangement overcomes many of the above noted disadvantages and enables connectors to be more densely populated, i.e. more connection points per unit area, GOLD DOT connectors have several shortcomings. For example, the connection of coaxial conductors is not accommodated and in-line filters, are not accommodated. Further, the capability to handle substantial electrical currents is not available. In addition, the clamping mechanism and related structure needed to withstand deformation and uniformly distribute the required clamping force for the mating connector halves is generally large and heavy. Since at least one mating part is made of flexible material and precise alignment is imperative, more weight and parts are required. Another weight and size penalty is suffered when ceramics, such as alumina, are used in mating parts. These parts must be soldered or bonded to a metal base to survive operating conditions. Also, the obverse side of either of the parts populated with GOLD DOTS, or the mating part with gold pads, cannot be used for mounting components.